Piston assemblies of internal combustion engines have a piston with annular grooves and sealing elements contained within each groove. One of the sealing elements may be a split compression ring. The axial width of the compression ring and associated groove may be reduced to reduce contact areas between the compression ring and a cylinder bore side wall, thereby reducing friction between the two surfaces. The dimensions of the compression ring and groove may be limited based on manufacturability and other factors, thereby limiting the reduction in friction.